Rod-Cone interaction is being studied in the human observer by means of psychophysical procedures and by means of intracellular recording in the retina of coldblooded vertebrates. To date, psychophysical results show that: 1. the influence of cones upon rod signals is qualitatively different during light adaptation as opposed to the earliest stages of dark adaptation; 2. scotopic flicker is mediated by two different channels; a very low frequency channel (less than 3 hz) which receives very little cone contribution and a relatively high frequency channel (5-12 hz) which receives both rod and cone contibutions; 3. the influence of a small (40') rod detected stimulus upon cone threshold can be described by a signal-to-noise mechanism. To date, neurophysiological results in the mudpuppy retina show that all types of postreceptor neurons receive a qualitatively similar input from both rods and cones, thus confirming the data of Fain (1975). Current experimentation is assessing the utility of a signal-to-noise model in describing various types of rod-cone interaction as assessed by both phychophysical and neurophysiological procedures.